Enantioselective Total Syntheses of (+)-Ganocin A and (-)-Cochlearol B

Herein, we report the total syntheses of (+)-ganocin A and (-)-cochlearol B, featuring pentacyclic skeletons, in optically active forms. We utilized asymmetric Corey-Bakshi-Shibata reduction, phenolic oxidative cyclization, the intramolecular radical cyclization-benzylic oxidative cyclization sequence, and intramolecular [2 + 2] photocycloaddition. These key steps enabled enantioselective access with the longest linear sequence of 17 steps and 9% overall yield for (+)-ganocin A and with 16 steps and 9% overall yield for (-)-cohlearol B.

Development of a Chiral N-Alkoxyamide Strategy and Application to the Asymmetric Total Synthesis of Fasicularin

The asymmetric total synthesis of fasicularin by a chiral N-alkoxyamide strategy is reported. Incorporation of the chiral alkoxy group onto an amide nitrogen changes the original reactivity of the amide, enabling two key transformations: aza-spirocyclization and the reductive Strecker reaction. DFT calculations indicate that pyramidalization of the N-alkoxyamide nitrogen is crucial to produce a cyclic hemiaminal in equilibrium, which undergoes aza-spirocyclization. The chiral alkoxy group is also used as a stereocontrol element to establish two consecutive stereocenters. The iridium-catalyzed reductive Strecker reaction of the N-alkoxylactam provides the aminonitrile with high diastereoselectivity.

Stereoselective Synthesis of the Decahydroquinoline Alkaloid cis-

The first enantioselective synthesis of two C-5 diastereomers of the proposed structure of the decahydroquinoline alkaloid cis-195J has been achieved. The key step of our strategy is the highly stereoselective vinylogous Mukaiyama-Mannich reaction (VMMR), which gave rise to the first two stereogenic centers at the ring fusion with excellent diastereo- and enantiocontrol. Through alkyne cyclization and enamine reduction the correct cis-configuration between C-2, C-4a, and C-8a in the decahydroquinoline backbone was established. Subsequently, a radical cyclization of a tethered alkyl iodide onto the enoate assembled the bicyclic cis-decahydroquinoline as a mixture of two C-5 diastereomers. Further elaboration of the C-5 side chain eventually provided both diastereomers of cis-195J, which were readily separated, and their constitution and configuration were thus unambiguously proven for the first time.

Iridium-catalyzed reductive Ugi-type reactions of tertiary amides

Amides are ubiquitous in the fine chemical, agrochemical and pharmaceutical industries, but are rarely exploited as substrates for homologous amine synthesis. By virtue of their high chemical stability, they are essentially inert to all but the harshest of chemical reagents and to the majority of chemical transformations routinely used in organic synthesis. Accordingly, the development of chemoselective carbon−carbon bond-forming methodologies arising from the functionalization of the amide functionality should find widespread use across academia and industry. We herein present our findings on a series of Ugi-type reactions of tertiary amides enabled by an initial chemoselective iridium-catalyzed partial reduction, followed by reaction with isocyanide and (thio)acetic acid or trimethylsilyl azide, thus providing a multicomponent synthesis of α-amino (thio)amide or α-amino tetrazole derivatives. The reductive Ugi-type reactions are amenable to a broad range of amides and isocyanides, and are applicable to late-stage functionalization of various bioactive molecules and pharmaceutical compounds.

Chemical transformation of amides is normally occurring under harsh conditions. Here, the authors report a mild iridium-catalyzed reductive Ugi-type coupling of tertiary amides, isocyanides and (thio)acetic acid or trimethylsilyl azide to give homologous, bioactive amine products.

The iridium-catalysed reductive coupling reaction of tertiary lactams/amides with isocyanoacetates

A catalytic reductive addition of isocyanoacetates to tertiary lactams/amides has been developed. This one-pot procedure involves Ir-catalysed partial reduction of lactams/amides and sequential chemoselective addition of isocyanide group in isocyanoacetates and produces 5-methoxyoxazoles in moderate to excellent yields.

Chemoselective direct reductive trifluoromethylation of amides: a flexible access to functionalized α-trifluoromethylamines

A one-pot method is reported for the direct transformation of secondary amides to α-trifluoromethylamines.

Total synthesis of complex alkaloids by nucleophilic addition to amides

This mini review focuses on the recent progress of total synthesis of complex alkaloids based on the nucleophilic additions toN-alkoxyamides, tertiary amides and secondary amides.

Recent advances in the intramolecular Mannich reaction in natural products total synthesis

This review focuses on selected applications of the intramolecular Mannich reaction as a key step in the total synthesis of natural products (2000–2017).

Enantioselective Total Synthesis of (+)-Gephyrotoxin 287C

A synthesis of (+)-gephyrotoxin 287C using (S)-phenylglycinol-derived tricyclic lactam 7 as the starting enantiomeric scaffold is reported. From the stereochemical standpoint, the key steps are the generation of the DHQ C-5 stereocenter by hydrogenation of the C-C double bond, removal of the chiral inductor to give a cis-DHQ, introduction of the DHQ C-2 substituent, completion of the (Z)-enyne moiety, and generation of the C-1 stereocenter during closure of the pyrrolidine ring.

Tertiary amine synthesis via reductive coupling of amides with Grignard reagents

A new iridium catalyzed reductive coupling reaction of Grignard reagents and tertiary amides affording functionalised tertiary amine products is described.

A new iridium catalyzed reductive coupling reaction of Grignard reagents and tertiary amides affording functionalised tertiary amine products via an efficient and technically-simple one-pot, two-stage experimental protocol, is reported. The reaction – which can be carried out on gram-scale using as little as 1 mol% Vaska's complex [IrCl(CO)(PPh₃)₂] and TMDS as the terminal reductant for the initial reductive activation step – tolerates a broad range of tertiary amides from (hetero)aromatic to aliphatic (branched, unbranched and formyl) and a wide variety of alkyl (linear, branched), vinyl, alkynyl and (hetero)aryl Grignard reagents. The new methodology has been applied directly to bioactive molecule synthesis and the high chemoselectivity of the reductive coupling of amide has been exploited in late stage functionalization of drug molecules. This reductive functionalisation of tertiary amides provides a new and practical solution to tertiary amine synthesis.

Direct transformation of amides: a one-pot reductive Ugi-type three-component reaction of secondary amides

An efficient reductive Ugi-type reaction employing common secondary amides as starting materials has been established. The reaction exhibited a broad substrate scope, good chemoselectivity and functional group tolerance.

Aza-Knoevenagel-type condensation of secondary amides: direct access to N-monosubstituted β,β-difunctionalized enamines

An efficient approach toN-monosubstituted β,β-difunctionalized enamines, a class of versatile building blocks for the synthesis of bioactive compounds, is reported.

The ‘Ireland’ one-pot alcohol oxidation coupling reactions: celebrating 30 years of diverse synthesis

The Ireland one-pot oxidative coupling reaction is reviewed on the occasion of its 30^th anniversary.